Solanum dennekense
Not known
Northeastern and eastern Africa in Ehtiopia, Somalia, Kenya, and Tanzania; growing in grassland, savanna, roadsides or edges of fields on well-drained sandy soil; 1200 – 2000 m elevation.
Solanum dennekense is a member of the Old World Clade within the Leptostemonum Clade (the spiny solanums; Levin et al. 2006); within that group is is a member of the Arundo clade, alongside its close relative S. arundo.(Vorontsova et al. 2013).
Friis, I. 2006. Solanaceae. In: I. Hedberg et al. (eds.), Flora of Ethiopia and Eritrea 5: 103 – 160. Addis Ababa University. Addis Ababa, Ethiopia and Uppsala University, Uppsala, Sweden.
Friis, I. 2006. Solanum. In: M. Thulin (ed.), Flora of Somalia 3: 206-219. Royal Botanic Gardens, Kew, United Kingdom.
Jaeger, P.-M.L. 1985. Systematic studies in the genus Solanum in Africa. PhD thesis, University of Birmingham, United Kingdom.
Levin, R.A., N.R. Myers, & L. Bohs 2006. Phylogenetic relationships among the "spiny" solanums (Solanum subgenus Leptostemonum). Amer. J. Bot. 93: 157-169.
Smith, G. F., and E. Figueiredo. 2011. Responsible species description: a change of attitude is needed to facilitate and improve access to biological material. Taxon 60: 1549-1551.
Vorontsova, M. S., S. Stern, L. Bohs, and S. Knapp. 2013. African spiny Solanum (subgenus Leptostemonum, Solanaceae): a thorny phylogenetic tangle. Bot. J. Linn. Soc. 173: 176-193. doi:10.1111/boj.12053
Solanum dennekense is a robust shrub with entire ovate pubescent leaves, white stems, hooked prickles on its stems and straight prickles on its leaves, and bright yellow fruits up to 3.5 cm in diameter that dry hard and bony. Most collections are made from weedy and fertile roadside plants only ca. 1 m tall, but in undisturbed open areas these can develop into trees ca. 6 m tall (M.S. Vorontsova, pers. obs.). The sap is aromatic (fide Tanner 4284). Solanum gillettii has been placed under S. arundo by Jaeger (1985) but under S. dennekense by Friis (2006a, 2006b); we agree with the latter opinion.
Solanum dennekense and the more common and largely sympatric S. arundo form the Arundo clade (Fig. 3 in Vorontsova et al. 2013), sharing the curved stem and straight leaf spines, tough yellow pericarp, and white stems. Solanum dennekense occupies wetter environments at higher elevations and can be distinguished from S. arundo by its ovate entire (to obscurely lobed) leaves more than 2.5 cm wide (versus elliptic clearly lobed leaves less than 2.5 cm wide in S. arundo), and leaf prickles 2-5 mm long (versus 5-15 mm in S. arundo).
We have been unable to locate any duplicates of the type collection of S. dennekense, so have here selected a neotype that is from a similar habitat (S. Demissew, pers. comm.) and is in the national herbarium of Ethiopia (see Smith & Figuieredo 2011 for best practice).
Of the two syntype collections cited in the description of Solanum ogadense (Keller s. n. and Ruspoli & Riva 342 (239), FT [FT003067]) the Keller s. n. duplicate at Z (Z000031052) is chosen as the lectotype due its better preservation status; no herbaria were cited for this collection in the protologue.